Relationship between litters per sow per year sire breeding values and sire progeny means for farrowing rate, removal parity and lifetime born alive.

The objective of this study was to determine the relationship between individual sire estimated breeding values (EBV) for litters/sow/year (LSY) and sire progeny means for farrowing rate (FR), removal parity and lifetime born alive (LTBA). Genetic parameters and breeding values were estimated using ASREML. The heritability estimate for LSY was 0.11. When all sires with 10 or more daughters with records were included in the analysis, Spearman rank correlations between the sire's LSY EBV and the sires' daughter means for FR, removal parity and LTBA were 0.49, 0.23 and 0.25 (p < 0.01). The sire EBV for LSY was favourably correlated with sires' daughter means for all three traits. This provides evidence that selecting sires with high EBV for LSY could improve herd FR, removal parity and LTBA. By including LSY as part of the selection criterion, the LTBA may be indirectly improved. The positive genetic correlation between LTBA and LSY may be a result of the improved longevity of sows with greater LSY compared with sows with lower LSY. The relationships between LSY and FR, removal parity and LTBA are strongly supported by the correlations between the sire progeny means for each trait and the sire LSY EBV.

Genetic relationship between purebred and crossbred sow longevity.

BACKGROUND: The overall breeding objective for a nucleus swine selection program is to improve crossbred commercial performance. Most genetic improvement programs are based on an assumed high degree of positive relationship between purebred performance in a nucleus herd and their relatives' crossbred performance in a commercial herd. The objective of this study was to examine the relationship between purebred and crossbred sow longevity performance. Sow longevity was defined as a binary trait with a success occurring if a sow remained in the herd for a certain number of parities and including the cumulative number born alive as a measure of reproductive success. Heritabilities, genetic correlations, and phenotypic correlations were estimated using THRGIBBS1F90. RESULTS: Results indicated little to no genetic correlations between crossbred and purebred reproductive traits. This indicates that selection for longevity or lifetime performance at the nucleus level may not result in improved longevity and lifetime performance at the crossbred level. Early parity performance was highly correlated with lifetime performance indicating that an indicator trait at an early parity could be used to predict lifetime performance. This would allow a sow to have her own record for the selection trait before she has been removed from the herd. CONCLUSIONS: Results from this study aid in quantifying the relationship between purebred and crossbred performance and provide information for genetic companies to consider when developing a selection program where the objective is to improve crossbred sow performance. Utilizing crossbred records in a selection program would be the best way to improve crossbred sow productivity.

Feed efficiency effects on barrow and gilt behavioral reactivity to novel stimuli tests.

Increasing feed efficiency is an important goal for improving sustainable pork production and profitability for producers. To study feed efficiency, genetic selection based on residual feed intake (RFI) was used to create 2 divergent lines. Low-RFI pigs consume less feed for equal weight gain compared to their less efficient, high-RFI counterparts. Therefore, our objective was to assess how a pig's behavioral reactivity toward fear-eliciting stimuli related to RFI selection and improvement of feed efficiency. In this study, behavioral reactivity of pigs divergently selected for RFI was evaluated using human approach (HAT) and novel object (NOT) tests. Forty low-RFI and 40 high-RFI barrows and gilts ( = 20 for each genetic line; 101 ± 9 d old) from ninth-generation Yorkshire RFI selection lines were randomly selected and evaluated once using HAT and once using NOT over a 2-wk period utilizing a crossover experimental design. Each pig was individually tested within a 4.9 × 2.4 m test arena for 10 min; behavior was evaluated using live and video observations. The test arena floor was divided into 4 zones; zone 1 being oral, nasal, and/or facial contact with the human (HAT) or orange traffic cone (NOT) and zone 4 being furthest from the human or cone and included the point where the pig entered the arena. During both HAT and NOT, low-RFI pigs entered zone 1 less frequently compared to high-RFI pigs ( ≤ 0.03). During NOT, low-RFI pigs changed head orientation more frequently ( = 0.001) but attempted to escape less frequently (low-RFI = 0.97 ± 0.21 vs. high-RFI = 2.08 ± 0.38; = 0.0002) and spent 2% less time attempting to escape compared to high-RFI pigs ( = 0.04). Different barrow and gilt responses were observed during HAT and NOT. During HAT, barrows spent 2% more time within zone 1 ( = 0.03), crossed fewer zone lines ( < 0.0001), changed head orientation less frequently ( = 0.002), and froze less frequently compared to gilts ( = 0.02). However, during NOT, barrows froze more frequently ( = 0.0007) and spent 2% longer freezing ( = 0.05). When the behavior and RFI relationship was examined using odds ratios, decreasing RFI by 1 kg/d decreased the odds of freezing by 4 times but increased the odds of attempting to escape by 5.26 times during NOT ( ≤ 0.04). These results suggest that divergent selection for RFI resulted in subtle behavioral reactivity differences and did not impact swine welfare with respect to responses to fear-eliciting stimuli.

Using classification trees to detect induced sow lameness with a transient model.

Feet and legs issues are some of the main causes for sow removal in the US swine industry. More timely lameness detection among breeding herd females will allow better treatment decisions and outcomes. Producers will be able to treat lame females before the problem becomes too severe and cull females while they still have salvage value. The objective of this study was to compare the predictive abilities and accuracies of weight distribution and gait measures relative to each other and to a visual lameness detection method when detecting induced lameness among multiparous sows. Developing an objective lameness diagnosis algorithm will benefit animals, producers and scientists in timely and effective identification of lame individuals as well as aid producers in their efforts to decrease herd lameness by selecting animals that are less prone to become lame. In the early stages of lameness, weight distribution and gait are impacted. Lameness was chemically induced for a short time period in 24 multiparous sows and their weight distribution and walking gait were measured in the days following lameness induction. A linear mixed model was used to determine differences between measurements collected from day to day. Using a classification tree analysis, it was determined that the mean weight being placed on each leg was the most predictive measurement when determining whether the leg was sound or lame. The classification tree's predictive ability decreased as the number of days post-lameness induction increased. The weight distribution measurements had a greater predictive ability compared with the gait measurements. The error rates associated with the weight distribution trees were 29.2% and 31.3% at 6 days post-lameness induction for front and rear injected feet, respectively. For the gait classification trees, the error rates were 60.9% and 29.8% at 6 days post-lameness induction for front and rear injected feet, respectively. More timely lameness detection can improve sow lifetime productivity as well as animal welfare.

Evaluation of mechanical and thermal nociception as objective tools to measure painful and nonpainful lameness phases in multiparous sows.

The objective of this study was to quantify pain sensitivity differences using mechanical nociception threshold (MNT) and thermal nociception threshold (TNT) tests when sows were in painful and nonpainful transient lameness phases. A total of 24 mixed parity crossbred sows (220.15 ± 21.23 kg) were utilized for the MNT test, and a total of 12 sows (211.41 ± 20.21 kg) were utilized for the TNT test. On induction day (D0), all sows were anesthetized and injected with Amphotericin B (10mg/mL) in the distal interphalangeal joint space in both claws of one randomly selected hind limb to induce transient lameness. Three days were compared: (1) D-1 (sound phase, defined as 1 d before induction), (2) D+1 (most lame phase, defined as 1 d after induction), and (3) D+6 (resolution phase, defined as 6 d after induction). After completion of the first round, sows were given a 7-d rest period and then the procedures were repeated with lameness induced in the contralateral hind limb. During the MNT test, pressure was applied perpendicularly to 3 landmarks in a randomized sequence for each sow: 1) middle of cannon on the hind limb (cannon), 2) 1 cm above the coronary band on the medial hind claw (medial claw), and 3) 1 cm above the coronary band on the lateral hind claw (lateral claw). During the TNT test, a radiant heat stimulus was directed 1 cm above the coronary band. The data were analyzed using the MIXED procedure in SAS with sow as the experimental unit. Differences were analyzed between sound and lame limbs on each day. For the MNT test, pressure tolerated by the lame limb decreased for every landmark (P < 0.05) when comparing D-1 and D+1. The sound limb tolerated more pressure on D+1 and D+6 than on baseline D-1 (P < 0.05). Thermal stimulation tolerated by the sound limb did not change over the 3 d (P > 0.05). However, the sows tolerated less heat stimulation on their lame limb on D+1 compared to D-1 levels (P < 0.05). Both MNT and TNT tests indicated greater pain sensitivity thresholds when sows were acutely lame.

Validation of a lameness model in sows using physiological and mechanical measurements.

The objective of this study was to develop a validated, transient, chemically induced lameness model in sows using subjective and objective lameness detection tools. Experiment 1 determined an effective joint injection technique based on volume and placement of dye using feet collected from 9 finisher pigs and 10 multiparity cull sow carcasses. Experiment 2 confirmed the injection technique in live animals and produced a transient clinical lameness in 4 anesthetized sows injected with amphotericin B (15 mg/mL) in the distal interphalangeal joints of the claw. Clinical lameness was assessed by a categorical lameness scoring system, and a postmortem visual confirmation of joint injection technique was obtained. In Exp. 3, 6 sows were injected with 0, 10, or 15 mg/mL amphotericin B in either the left or right hind foot and were monitored until clinical resolution. Treated sows demonstrated elevated clinical lameness scores. These changes resolved by 7 d after lameness induction. Control sows injected with sterile saline developed a clinical lameness score of 0.5, which resolved 72 h post injection. In Exp. 4, 36 sows were injected with 10 mg/mL amphotericin B in 1 of 4 injection sites (left front claws, right front claws, left rear claws, and right rear claws). All injected sows exhibited a decrease in maximum pressure, stance time, and number of sensors activated on the GaitFour (P < 0.05) sensor system. A static force plate also demonstrated a decrease in weight (kg) being placed on the injected foot when all feet were injected (P ≤ 0.05). Injection of amphotericin B induced a predictable acute lameness that resolved spontaneously and is an effective method to model lameness in sows.